When one traveler's suitcase gets lost, they lose everything because all their stuff is stored in a single bag. If a group travels and distributes each person's belongings throughout every suitcase, one lost suitcase won't leave anyone with absolutely nothing. Redditor whedonmoffatparadigm explains:

At the very least, make sure each case contains at least one complete outfit for each person. That way, if one of the cases is lost, no one will be completely without a change of clothes. If you're travelling alone and are checking a bag, take a change of clothes in your carry on, for the same reason. At the very least, take a change of underwear in your carry on.

Basically, pack your bags kind of like a RAID 5 or 6 array and you can still recover easily from a loss. This might make packing and unpacking kind of a pain, but it shouldn't be too much of a problem for families.